End of summer to follow with variable weather

September 20, 2012

Saturday marks the official end of the Northern Hemisphere's astrological summer, and forecasts by the National Weather Service in Gaylord suggest summer temperatures will follow suit.

According to statistical averages dating back to 1916, the summer of 2012 was the second warmest on record for Northeast Michigan. June saw average temperatures of 65.9 degrees in Alpena, or 3.8 degrees above the norm, with highs well into the 80s and occasionally the 90s toward the end of the month; July's average of 71 was 3.6 degrees above the annual standard; and August's 67.2-degree average was 1.8 above normal. Temperatures didn't hold through September, which started with a few 80- and 90-degree days and cooled to night lows in the 40s more recently, which meteorologist Dave Lawrence said is historically more typical for this time of year.

"At this point, temperatures for the month are still above normal. We have had a couple of cool days, of course, but that's not going to offset how warm it was for the start of the month," he said. "Almost for the past 10 years, I think with one exception, we've had very warm falls, especially during the months of September and October, so this seems a little different, but it's actually very normal for what typically used to happen around here a lot more."

Lawrence expects cooler temperatures in the 50s and 60s to last through at least the first half of next week, with a possible overnight frost at some point, then moderate somewhat thereafter. In the long run, he thinks the pattern of oscillating temperatures will set up climate conditions for the rest of the fall.

"I'd call it 'variable,' for the fall. We've seen a lot of warm weather for the past couple falls ... but I think, we're already seeing signs of it, but this one has a much higher potential to be up and down. With that, it's going to be a bit more stormy as well," he said. "There's no doubt about it, we are going to see more warm days. That's what fall is all about around here, is up and down, but I really think this year is going to be a lot more pronounced. We're already seeing signs of it - we just had that quick burst when it warmed a little bit (Wednesday) and then we're having another quick (cold spell) this weekend - but we'll do that a few more times, I'm sure, as we go through the next couple months."

That said, he does not expect snow until mid-October at the earliest, as Alpena has only seen a handful of September snowfalls in the last 100 years.

Lawrence attributed the cold temperatures to a strengthening subtropical jet stream that forced warm high pressure systems west from the plains to the west coast, leaving the Midwest in a blanket of cold air from the north.

"Weather is basically all about balancing temperatures across the globe. You have to have warm air moving north and cold air moving south to balance it out, so eventually it's inevitable: if it gets warm for too long, things are going to shift," he said. "Part of that shift might be attributed to the development of El Nino out of the Pacific a little bit."

He called it a "very normal" seasonal shift, and though he believed it was too soon to make any confident predictions about winter, he guessed, based on records of similar years, that the state will see slightly earlier snows this fall than in the past three years.